ash: Use the easy-resize window targeter for some window containers.

BUG=318879
R=ben@chromium.org

Review URL: https://codereview.chromium.org/125333004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243286 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243286
aura: Add a window-targeter for windows with hit-test masks.

Use the masked-window targeter for the touch-selection handlers. Subsequent
patches will install similar targeters for the other windows that use hit-test
masks, which will allow getting rid of some hit-test mask related API from aura
and views.

BUG=318879
R=ben@chromium.org

Review URL: https://codereview.chromium.org/122573005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243287 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243287